I have not looked too closely at other banks but I get the impression that the market is starting to think that their expectation of economic meltdown, and therefore banks being at the top of their cycle, may have been a bit premature. Add that to the RBS PR department working overtime the last few weeks, plus the pre-close trading statement, and I think a bit of extra momentum is being added to RBS.
Could also be that new positions are being taken for the beginning of the year . If a fund has a losing stock then they flog it off and buy something with momentum so they can report an end of year selection which are in the positive to their clients. Cynical but apparently true.